Lpc2000

I would guess this has more to do with legal liability.  If you
make an offer in a global forum, you're offering it to everyone
everywhere in the world and you will be expected to comply with
their laws in doing so.  If you say the offer is good only in a
limited area, you limit the laws with which you must comply.

So, to offer this to U.S. residents only means that they just
need to pass the offer by a team of U.S. law aware lawyers to
ensure that it's good.  To offer it to the whole world, you'd
have to retain legal counsel in every country in the world to
review your proposal.  I'm pretty sure that would cost more than
$20K (USD).

So, since the idea of the contest is to come up with good app
notes, not to employ lawyers, they probably picked a limited
area for which they had free access to legal counsel.

For those in the U.S. you're probably familiar with the little
blurbs they add to the end of free prize contests where they
state that the offer is not valid in certain states because 
those specific states have some law preventing the contest from
being legal in their jurisdiction.  If all of the states in the
US can't even agree on how to make it legal to *give away for
free* some item, do you expect every country in the world to have
uniform laws on business contracts?

So, don't blame Philips, take issue with your local lawmakers
for being so silly. :)

Cheers,
David